• Takahiro Iwata, Kei Miyamoto, Akira Hioki, Kazunari Fushimi, Takatoshi Ohno, and Katsuji Shimizu.
• *Department of Orthopaedic Surgery, Ibi Kousei Hospital Departments of †Orthopaedic Surgery ‡Reconstructive Surgery for Spine, Bone, and Joint, Gifu University Graduate School of Medicine, Gifu, Japan.
• J Spinal Disord Tech. 2015 Jun 1;28(5):E270-6.

Study DesignA retrospective study of 58 patients undergoing cantilever transforaminal lumbar interbody fusion (c-TLIF).ObjectivesTo evaluate morphologic changes in the intervertebral foramen (IVF) on the side contralateral to spacer insertion in patients undergoing c-TLIF using plain x-ray films and computed tomography scan.Summary Of Background DataThe morphologic changes in the contralateral lumbar foramen in c-TLIF using unilateral insertion of spacers have not been well studied.Materials And MethodsFifty-eight consecutive patients with lumbar dysplastic changes or degenerative disk diseases underwent c-TLIF using 96 kidney-type spacers with local bone grafts. Radiographic findings (sagittal disk angle), computed tomography scan findings (coronal disk angle, disk height, foraminal height (FH), foraminal width, and cross-sectional area of IVF in contralateral lumbar foramen) were compared between preoperative period and 6 months after surgery. The correlations between contralateral lumbar foraminal dimensions and disk height, sagittal disk angle, and coronal disk angle were analyzed.ResultsAfter c-TLIF, sagittal angle, disk height, FH, foraminal width, and cross-sectional area of the IVF were significantly increased. Increase in posterior disk height showed a positive correlation with increases in FH, foraminal width, and cross-sectional area of IVF (r=0.235-0.511). However, the increase in sagittal disk angle showed a negative correlation with changes in foraminal width and cross-sectional area of IVF (r=-0.256 to -0.206).ConclusionsLumbar foraminal dimensions on the side contralateral to spacer insertion increased significantly after c-TLIF, suggesting that c-TLIF enables indirect decompression of the contralateral nerve root. Although increase in posterior disk height was shown to be an important factor to increase contralateral foraminal size, segmental lordosis was a risk factor for a decrease in contralateral foraminal size.

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